Effect of Steeping Corn with Lactic Acid on Starch Properties

Pasting and thermal properties of starch from corn steeped in the presence of lactic acid and at different steeping times (8, 16, 24, 32, and 40 hr) were investigated. Corn kernels were steeped at 52°C with 0.2% (w/v) SO₂ and with and without 0.5% (v/v) lactic acid. The isolated starch obtained by corn wet‐milling was characterized by determining starch recoveries, retrogradation, and melting transition properties of the lipid‐amylose complex by differential scanning calorimetry (DSC), and pasting properties by the Rapid Visco Analyser (RVA). Damaged granules and the starch granule size were determined by using microscopic techniques. Starches from corn steeped in the presence of lactic acid (LAS) were compared with control starch (CS) steeped without lactic acid. Greater starch recoveries were obtained for LAS samples than for CS samples, and practically no damaged starch was present in the former preparations. The presence of lactic acid affected the RVA profiles and steeping time affected the viscosities of the starch suspensions. In general, the RVA parameters of LAS suspensions were lower than those of CS suspensions. No great modification of the thermal properties was observed; only a slight decrease in amylopectin retrogradation and in the melting enthalpy of the amylose‐lipid complex was observed. Hydrolysis of the starch during steeping seems the most probable explanation to the starch modifications produced by lactic acid addition.     

Batch Steeping of Corn: Effects of Adding Lactic Acid and Sulfur Dioxide at Different Times on Starch Yields,Protein Contents,and Starch Pasting Properties

The effect of adding lactic acid and sulfur dioxide at different times from the start of batch steeping on corn starch yields was studied. Five commercial hybrids were steeped with 0.5% lactic acid or 0.2% sulfur dioxide added over the first 15 hr of steeping and wet-milled following a 100-g corn wet-milling procedure. No significant differences were observed in starch yields when lactic acid was added to the steep solution (SO₂ and water) from 0 hr (start of steeping) to 15 hr. Addition of SO₂ to the steep solution (lactic acid and water) resulted in significantly higher average starch yields when SO₂ was added between 5 and 15 hr compared with addition at 0 hr (SO₂ and lactic acid for full 24 hr of steeping). Based on the results of the first experiment, a second experiment was done in which one of five original hybrids was steeped for 24 hr, during which lactic acid or SO₂ was added until 23.9 hr (i.e., 5 min before milling) after the start of steeping. Similar results were found in the second experiment. Residual protein in starch samples did not exceed 0.85%. Steepwater protein content decreased with delays (16–20 hr) in adding either chemical to the steep solution. A significant effect on starch pasting properties of chemicals and duration of chemicals in steep-water was observed. Testing these findings using a larger scale (1,000 g) corn wet-milling procedure produced results similar to those obtained with the 100-g corn wet-milling procedure.     

Effect of Lactic Acid on Protein Solubilization and Starch Yield in Corn Wet‐Mill Steeping: A Study of Hybrid Effects

To better understand the role of lactic acid (LA) in corn wet‐milling, steeping studies were performed on different yellow dent corn hybrids using four different solutions containing LA, sulfur dioxide (SO₂), a combination of LA and SO₂, or no added chemicals. Although there was variation in protein solubilization among the hybrids, protein release was consistently higher when LA was included in the steepwater than when it was excluded (both with and without SO₂). Several groups have reported that starch recoveries are improved when steepwater contains LA. To explore the relationship between protein solubilization and starch yield as effected by LA, several yellow dent hybrids were steeped in 0.20% SO₂ and 0.50% LA‐0.20% SO₂ solutions and milled to recover starch by a 100‐g laboratory corn wet‐milling procedure. In all instances, both starch yields and protein solubilization were enhanced in solutions containing LA. These results support the hypothesis that direct dissolution of the endosperm protein matrix by LA contributes to the improved starch recoveries.     

Reducing Ammonia Losses by Adding FeCl3 During Composting of Sewage Sludge

The release of ammonia nitrogen during composting of sewage sludge mixed with a lignocellulosic bulking agent leads to a reduction in the agronomic value of the final compost and to harmful effects on the environment. We propose adding a cheap salt FeCl3 which can be used without special precaution to reduce ammonia losses by decreasing pH conditions. An in-vessel co-composting experiment was conducted in a large reactor (100 L) in which FeCl3 was added to sludge mixed with a bulking agent (pine shavings and sawdust) and compared with a control mixture without FeCl3. Temperature, oxygen consumption and pH were monitored throughout the composting of both mixtures. The final balance of organic matter, organic and inorganic nitrogen permitted to conclude that the addition of FeCl3 reduced nitrogen loss (by a factor of 2.4 in relation to the control) and increased mineralisation of the organic nitrogen by 1.6.     

Effect of Temperature and Steeping Time on Calcium and Phosphorus Content in Nixtamalized Corn Flours Obtained by Traditional Nixtamalization Process

This report shows the effect of temperature (72, 82, and 92°C) during the cooking stage and steeping time (0, 1, 3, 5, 7, 9, 11, 13, and 15 hr) on calcium and phosphorus contents in nixtamalized corn flours obtained by the traditional nixtamalization process (NCF). In addition, calcium and phosphorus contents in industrial nixtamalized corn flours were analyzed for comparative purposes. Atomic absorption spectroscopy and UV‐vis spectroscopy methods were used to study the calcium and phosphorus contents as well as the Ca²⁺/P ratio in NCF and industrial nixtamalized corn flours. Additionally, deposition and identification of calcium compounds in the nixtamalized corn pericarp were analyzed by low‐vacuum scanning electron microscopy, energy dispersive spectrometry, and X‐ray diffraction techniques. Dry matter loss in NCF is also reported. As the temperature increased, Ca²⁺ content was enhanced, while the phosphorus content decreased with statistical differences (P ≤ 0.05) between thermal treatments. Ca²⁺ content in industrial nixtamalized corn flours was significantly lower (P ≤ 0.05) than that of NCF. On the other hand, no statistical differences (P ≤ 0.05) were found between phosphorus content in commercial nixtamalized corn flours and NCF. Calcium compounds, identified as calcite, were detected in corn pericarp. Statistical differences (P ≤ 0.05) were observed in phosphorous content in NCF obtained at different cooking temperatures. In addition, a decrease in phosphorus levels significantly correlated with the steeping time at 92°C (r = –0.91). At 72, 82, and 92°C, the average Ca²⁺/P ratio in NCF was 0.45 ± 0.03, 0.61 ± 0.05, and 0.82 ± 0.05, respectively, indicating a correlation between this parameter and the cooking temperature. However, no correlation was found between the Ca²⁺/P ratio and the steeping time. This behavior is attributed to calcium attached to corn kernel. In commercial nixtamalized corn flours, the Ca²⁺/P ratio was significantly lower (P ≤ 0.05) than that of NCF. There was a significant correlation (P ≤ 0.01) between dry matter loss and steeping time (r = 0.99) in NCF, this fact influenced the Ca²⁺/P ratio due to the calcium attached to pericarp. At 82 and 92°C, maximum values of Ca²⁺/P ratio were detected in NCF at 7 hr of steeping time and at 9 hr at 72°C. These results can be used with industrial purposes to assess a maximum calcium‐to‐phosphorus ratio, and at the same time, to avoid the loss of pericarp to increase the functional properties of NCF.     

Effect of Steeping Conditions (Sulfur Dioxide,Lactic Acid,and Temperature) on Starch Yield,Starch Quality,and Germ Quality from the Intermittent Milling and Dynamic Steeping Process (IMDS) for a Brazilian Corn Hybrid

Effect of lactic acid, SO₂, temperature, and their interactions were assessed on the dynamic steeping of a Brazilian dent corn (hybrid XL 606) to determine the ideal relationship among these variables to improve the wet‐milling process for starch and corn by‐products production. A 2×2×3 factorial experimental design was used with SO₂ levels of 0.05 and 0.1% (w/v), lactic acid levels of 0 and 0.5% (v/v), and temperatures of 52, 60, and 68°C. Starch yield was used as deciding factor to choose the best treatment. Lactic acid added in the steep solution improved the starch yield by an average of 5.6 percentage points. SO₂ was more available to break down the structural protein network at 0.1% than at the 0.05% level. Starch‐gluten separation was difficult at 68°C. The lactic acid and SO₂ concentrations and steeping temperatures for better starch recovery were 0.5, 0.1, and 52°C, respectively. The Intermittent Milling and Dynamic Steeping (IMDS) process produced, on average, 1.4% more starch than the conventional 36‐ hr steeping process. Protein in starch, oil content in germ, and germ damage were used as quality factors. Total steep time can be reduced from 36 hr for conventional wet‐milling to 8 hr for the IMDS process.     

N+注入诱变高自溶度的乳酸菌突变株

通过N+注入方式对乳酸菌唾液链球菌嗜热亚种GS1和德氏乳杆菌保加利亚亚种LD3进行诱变,获得自溶度较高的乳酸菌菌株。离子注入剂量为1×2.6×103～6×2.6×1013时,菌株的存活率曲线呈典型的马鞍型剂量-效应曲线,总突变率达到57%～74%。离子注入能量为50keV,最佳注入剂量为4×2.6×1013 ion/cm2,此时,菌体存活率为25%～33%。筛选得到的乳酸菌菌株,自溶度变化幅度在127.98%～-51.96%之间。得到2株自溶度显著提高的突变菌株,分别命名为LD3-A3和GS1-B13,与出发菌株相比其自溶度分别提高了127.98%和115.11%。经5次传代培养,突变株的自溶度和遗传性状比较稳定。结果表明离子注入诱变技术是一种理想的乳酸菌发酵剂菌种选育方法。     

Optimization of Temperature,Time, and Lactic Acid Concentration to Inactivate Lipoxygenase and Lipase and Preserve Phytase Activity in Barley (cv. Blenheim) During Soaking

A barley-soaking process was studied to find conditions that inactivate the prooxidative enzyme lipoxygenase and the lipolytic enzyme lipase but preserve phytase activity to develop possible procedures for production of barley products with potentially high mineral bioavailability and good oxidative stability. Lactic acid concentration, temperature, and soaking time were studied. The study was done using a multivariate experimental design. Lactic acid concentration varied between 0 and 1%, temperature varied between 45 and 70°C, and soaking time varied between 30 and 120 min. Although conditions under which lipoxygenase was inactivated were found, total inactivation of lipase was not obtained. Total lipoxygenase inactivation with <20% remaining lipase activity and >60% remaining phytase activity was reached after soaking in 1% lactic acid at suitable time-temperature combinations of 70–110 min and 53–58°C.     

减施化肥与不同有机肥配施对稻季土壤细菌群落结构的影响

为了研究减施化肥配施不同有机肥对稻麦轮作体系稻季土壤细菌群落结构的影响，采用Illumina高通量测序技术比较了单施化肥、配施菜籽饼和配施蚯蚓粪这3种施肥模式下稻季不同土层土壤环境因子、细菌群落结构变化特征。与单施化肥相比，配施有机肥显著提高各土层土壤有机质和电导率（EC）含量，配施菜籽饼增幅较大；显著增加各土层土壤氮磷钾养分含量，配施蚯蚓粪的土壤速效氮磷钾养分含量较高。配施有机肥提高土壤细菌Sobs指数和Shannon指数；前三位优势菌门，变形菌门（Proteobacteria）、酸杆菌门（Acidobacteria）、绿弯菌门（Chloroflexi）相对丰度分别达36.24%、18.30%、13.87%；配施有机肥对相对丰度小于1%的菌门影响较大。0-5cm土层土壤细菌群落结构主要受pH、TP影响；5-10cm土层土壤细菌群落结构主要受EC，TP、pH影响；10-15cm土层土壤细菌群落结构主要受TN、pH影响。配施有机肥通过改变土壤理化性质进而影响土壤细菌群落结构，特别是稀有菌群。     

Changes in the Phenolic Acid Content and Antioxidant Activity During Kernel Development of Corn (Zea mays L.) and Relationship with Mycotoxin Contamination

Corn grain production could be affected by several fungal pathogens responsible for the production of mycotoxins. The aims of this study were to determine the evolution of phenolic acids and total antioxidant activity (TAA) during kernel development and to evaluate their potential protective role in minimizing mycotoxin contamination in six corn genotypes (four open‐pollinated varieties and two hybrids) characterized by a wide array of kernel traits. TAA and free and cell wall‐bound phenolics showed significant differences among corn genotypes at different stages of development, with the highest values found at the beginning of kernel development. Ferulic, p‐coumaric, and caffeic acids were the main cell wall‐bound phenolic acids during kernel development, whereas chlorogenic acid was the main free phenolic acid. A significant negative correlation was observed between deoxynivalenol contamination at harvest maturity and free phenolic acids and TAA at the beginning of kernel development, whereas no significant correlation was observed with fumonisin contamination. In conclusion, free phenolic acids are evidently involved in the resistance mechanism toward deoxynivalenol contamination, whereas their role toward fumonisin contamination was not elucidated under field conditions, implying that components other than phenolic acids may be responsible for this latter type of resistance.     

秸秆深还不同年限对黑土腐殖质组成和胡敏酸结构特征的影响

秸秆深还(Corn stover deep incorporation,CSDI)指将作物秸秆深埋于土壤亚表层20~40 cm深处,用以解决秸秆焚烧和土壤肥力退化的可持续利用模式。本文以吉林农业大学玉米连作耕地试验田未施用秸秆和秸秆深还不同年限的土壤为研究对象,设置CK、CSDI(2014)、CSDI(2013)和CSDI(2012)共4种处理,分别代表未施入秸秆、2014年秸秆深还(深还第1年)、2013年秸秆深还(深还第2年)、2012年秸秆深还(深还第3年),研究秸秆深还不同年限对黑土腐殖质组成和胡敏酸结构特征的影响。通过腐殖质组成修改法提取富里酸(Fulvic acid,FA)、胡敏酸(Humic acid,HA)和胡敏素(Humin,HM),国际腐殖质协会(International Humic Substances Society,IHSS)推荐的方法提取HA样品,通过元素组成、红外光谱和差热分析测定HA结构。结果表明:与CK相比,秸秆深还1年后显著提高了土壤和腐殖质各组分有机碳含量,亚表层累积效果更明显,其土壤有机碳(SOC)、HA、FA和HM有机碳含量分别增加了23.7%、30.5%、27.3%和46.1%,但PQ值(HA在可提取腐殖物质的比例)没有显著变化;HA氧化度和缩合度降低明显,表层和亚表层(O+S)/C比值分别降低14.31%和14.68%,H/C比值分别增加27.74%和28.86%,脂族链烃和芳香碳含量增加,热稳定性降低,HA结构趋于简单化。随着年限增加,深还3年后SOC、FA和HM有机碳含量呈下降趋势,HA有机碳含量呈上升趋势,PQ值变化显著,HA缩合度、氧化度呈上升趋势,脂族性减弱,芳香性增强,HA结构趋于复杂化。说明随着年限增加,秸秆不断矿化分解,秸秆深还对土壤腐殖质组成和结构特征的影响效果减弱。     

不同浸提剂提取的土壤磷铝与油茶各器官磷铝含量的相关分析

采用Mehlich3、ASI、Bray、DTPA、HCl等5种浸提方法测定油茶林地土壤磷、铝含量,并分析其与叶片等器官磷、铝含量的关系。结果表明:ASI法提取的磷含量最高,平均值达4.12 mg/kg,Bray法提取的磷含量最低;铝提取量依次为HCl-AlBray-AlM3-AlASI-AlDTPA-Al。5种方法提取的磷、铝含量分别存在较好的正相关关系。油茶叶片的磷含量和铝含量最高,其中铝含量达14.22 g/kg,是其他器官铝含量的11.5~28.1倍。叶片磷含量与HCl-P、叶片铝含量与HCl-Al分别呈显著正相关。该研究表明0.01 mol/L HCl提取法具有应用于同时测定土壤磷、铝含量和评价其对油茶生物有效性的可行性。